Experimental investigation of the reflectivity of refractory dielectric materials in the vacuum ultraviolet spectral region

The paper deals with the results of experimental investigation of spectrally averaged group reflectivities $(R(\Delta\lambda))$ in a vacuum ultraviolet ($h\nu\sim10$ to $70$ eV) spectral range of commercial samples of high-temperature dielectric materials ($\alpha$-$\mathrm{Al}_2\mathrm{O}_3$, $\mathrm{Si}\mathrm{O}_2$, $\mathrm{BNC}$) under conditions of a prethreshold (prior to the beginning of developed surface evaporation) power density of probing radiation.